I have played both Cliff and Ernst, and there is nothing in the text that suggests Ernst is attracted to Cliff. However, I distinctly remember in the Mendes production Denis O’Hare adding a sexual subtext to lines like “We make a large whoopee,” etc. It made zero sense, but O’Hare is such a great actor that it somehow worked. When was that? 1998? Strange what we remember about plays we see.
Anyway, this is not the first professional production of Cabaret to have Cliff played by a black actor. I know of at least one other where it was done a few years ago in Chicago. If you’re going to have one of the principals played by POC, Cliff can be an interesting choice since he is the American and the stand-in for the audience.
I’m pretty sure there have been black Emcees and Sallys in major regional productions as well, although not often. Ultimately, you really can’t have all white principal casts anymore, so even when it doesn’t make sense historically, you have to find a way to have a diversify it.